HYDROGEOLOGICAL MAPPING OFKADUNA AND ITS ENVIRONS

ABSTRACTGroundwater is the main source of water for the people of Kaduna and its environs particularly in the rural areas. The purpose of this study is to assess the effects of waste dumps on the groundwater of Kaduna and its environs. The study area lies between latitudes 100 26' to 100 40'N and longitudes 70 19' to 70 33'E with a total surface area of 630km2. The major town in the study area is Kaduna which is the capital of Kaduna State.The area is underlain by the Crystalline Basement rocks. The dominant rock types are the migmatite-gneiss complex and the Older Granites which intruded the host gneissic rocks. Prolonged in-situ weathering of the Crystalline Basement rocks under tropical conditions has produced a sequence of unconsolidated material (laterites) whose thickness and lateral extent vary extensively. There are three major types of aquifers in the study area namely weathered overburden aquifer, fractured bedrock aquifer and the stream alluvial deposits aquifer. The three aquifers are interconnected and form one hydraulic system with unconfined water table. The depth to water table in hand-dug wells varied from 0.20m to 11.60m in the study area.Eighty-eight (88) hand-dug wells were studied and thirty-four (34) representative water samples were analysed in the laboratory. The results were compared with WHO (2006) and NAFDAC standards for drinking water.Results of physical parameters showed pH ranged from 4.83 to 7.80, electrical conductivity from 20-980µS/cm and TDS from 10-490mg/l. Results of the cations showed Na+ varied from 1.66-221.20mg/l, Ca2+ from 0.23-92.00mg/l, Mg2+ from 0.12-154.00mg/l, K+ from 0.72-71.48mg/l, Fe2+ from 0.02-0.22mg/l and Pb2+ from 0.18-0.95 mg/l. Results of the anions showed Cl- varied from 2.67-176.94 mg/l, SO42- from 1.00-250 mg/l, NO3-from 0.05-55.00mg/l ,CO32- from 4.80-50.40mg/l and HCO3- from 2.40-62.00mg/l. Result of the microbial analysis showed Cfu/ml varied from 80-240. The concentration values of the cations and anions (except Fe2+ and SO42-) exceeded the WHO (2006) and NAFDAC recommended standards for drinking water in some places particularly at Askolaye, Barnawa and Baba Sara. The dominant cation and anion in the groundwater are magnesium and chloride respectively. The water types are Mg-Cl, Ca-Mg-SO4 and Na- K waters.The high concentration of sodium and chloride in the water in some places in the study area could be from contamination by saline effluents or leachates from waste dumps. The relative high concentration of nitrate in the study area could be as a result of pollution from septic tanks and fertilizer.Waste dumps of serious environmental concern were observed at Fire Brigade, Tudun Nupewa, Tudun Wada, Hayin Banki, Ungwan Dossa, and Kawo. Downstream of River Kaduna around the factories at Kakuri is polluted with industrial waste. It is recommended that the factories located in Kaduna South should process their industrial wastes before discharging them into the river. Boreholes should be provided by government in rural areas to reduce groundwater contamination from anthropogenic activities. Also, the water from hand-dug wells in the area should be treated before drinking.